Individuals are often comfortable dealing with documents in hardcopy format. In general, hardcopy documents are easier to read, handle, and store than documents kept in the digital domain. However, privacy of personal identification information is a concern because the information can be easily read and transmitted from person to person. As such, there is a risk of documents containing personal identification information being seen by persons without authorization.
Methods exist to limit the amount of personal identification information that is visible on a hardcopy document. The emergence of electronic document processing systems has enhanced significantly the functional utility of plain paper and other types of hardcopy documents when the visible (or human readable) information they normally convey is supplemented by writing appropriate secured (or machine readable) digital data on the documents. Various methods of embedding machine readable code into documents in order to control the amount of information visible on a document have been tried, and are described in U.S. Pat. No. 4,728,984 entitled “Data Handling and Archiving System,” U.S. Pat. No. 5,982,956 entitled “Secure Method for Duplicating Sensitive Documents,” and U.S. Pat. No. 6,175,714 entitled “Document Control System and Method for Digital Copiers,” all of which are incorporated by reference in their entireties for the teachings therein.
Prior attempts to limit access to personal identification information offered access that is all or nothing. For example, a document contains no visible personal identification information, contains a plethora of visible personal identification information, or contains machine readable personal identification information to which access to is given to any individual with capabilities of encoding the personal identification information. Thus, there is a need in the art for documents that limit the amount of visible personal identification information and allow only those individuals who should have access to the information to view it. By replacing the human readable personal identification information with machine readable code that has been encrypted using public key cryptography, access to the personal identification information may be limited.